Abstract! Engineered nanomaterials (ENMs) are being increasingly used in industrial and biomedical applications. It is estimated that there are currently more than 1,800 nanomaterial-based products on the market, with more than 770 in the United States alone. This widespread use has raised concerns regarding the potential health hazards of ENMs. One important aspect of toxicity of ENMs is their interaction with the plasma membrane of mammalian cells. The plasma membrane is the first cellular entity that meets ENMs and has been suggested to play a major role in ENM-induced cytotoxicity. Over the past decade, a number of studies have utilized simple membrane models, such as phospholipid vesicles, to gain mechanistic information on ENM-membrane interactions. However, the plasma membrane is an asymmetric lipid structure with a diverse array of lipids and proteins; therefore, studies with simple membrane models do not provide a comprehensive understanding of ENM- membrane interactions in live cells. The current application aims to provide a mechanistic understanding of the role of membrane lipid asymmetry and membrane proteins, in modulating ENM-membrane interactions. Using vesicles that mimic the asymmetry of the cell plasma membrane, as well as biologically-relevant vesicles that are isolated from the membrane, this application aims to investigate the role of membrane asymmetry and membrane proteins in how ENMs with different surface properties and protein corona bind to the plasma membrane, internalize in cells, and alter plasma membrane structure and integrity. The information generated from this work is expected to elucidate the role of the plasma membrane structure and composition in ENM-membrane interactions, facilitate the development of more physiologically relevant membrane models for mechanistic studies, and reveal the role of particle physicochemical properties and protein corona in their interactions with the cell plasma membrane. The knowledge base created from this work will significantly enhance the fields of particle-mediated drug delivery and environmental health and safety of ENMs.